One long ago morning in California, as debate raged over the anti-immigration initiative known as Proposition 187, I walked into a coffee shop in the town of Selma, the "raisin capital of the world," to feel the pulse of the farmer.

From counter to booth, it was all gloom. If Prop. 187 passed, requiring legal residency for public schooling and other services, disaster was next, the farmers said: There would be no Mexican illegals to pick the crops.

I was about to leave when a grape grower with a Middle Eastern last name stopped me. Yes, 80% of his pickers came from Mexico without legal documents. Yes, these migrants were among the hardest working people on earth. But he was going to vote for Prop. 187 anyway.

"We need to send a message to these Mexicans that the state of California isn't for sale," he said. Then he added, with a touch of rural realpolitik, "Even if 187 passes, they're going to find a way to get to my fields."

What is it about immigration that drives America crazy mad, makes us forget who we are?

Peter Schrag takes up that question in "Not Fit for Our Society," a thoughtful, especially timely look at the spasms of anti-immigration that have defined our nation from the very beginning. He writes: "The history of American attitudes about immigration and immigration policy has long been a spiral of ambivalence and inconsistency, a sort of double helix, with strands of welcome and rejection wound tightly around one another."

How else to explain the paradox implicit in the anti-immigration rants of former Rep. Tom Tancredo (R-Colo.)? He's the grandson of a Sicilian immigrant whose "race" was once officially listed as among the most inferior in morals and intelligence of any group entering the U.S.

"If this book tells anything about that three-hundred-year narrative," Schrag writes, "it's that almost everything that's being said in the arguments for closing the border and shutting down immigration has been said before, often in literally the same terms and tones."

A longtime newspaper columnist, Schrag is an old-school digger and thinker who approaches immigration from the political left but never with a partisan's shrillness. Deftly, often powerfully, he traces the contradictions to our nation's DNA.

The Declaration of Independence stated that "All men are created equal." Puritan John Winthrop envisioned the new land as the "City upon a Hill," a beacon to the rest of the world. Who would fell the trees, clear the fields and plant the crops, if not the immigrant drawn by that light?

Yet we were also a place that saw itself as God's manifestation, a land of innocence and exceptionalism in a world of decadence. We could hardly allow such a place to be defiled by the dreg, the criminal, the anarchist, the too fertile. So it became that the noble Saxon forbid the German, and the German forbid the Irish, and the Irish forbid the Italian, and the Italian forbid the Jew, and the Jew forbid the Chinese, and the Chinese forbid the Mexican, and the Mexican forbid the Muslim.

We were a great melting pot. From forbidden to forbidder, it took but a generation or two.

In the late 1700s, as the U.S. vacillated from one of the world's most liberal naturalization laws to one that required 15 years of residency, Thomas Jefferson could be heard moaning about immigrants from foreign monarchies. The Rev. Lyman Beecher, the Lou Dobbs of the mid-1800s, railed against the Catholic hordes from Europe — the "contents of the poor house and the sweepings of the streets."

Soon, Boston would elect its first Irish-Catholic mayor.

Nativism is our most stubborn trait. Dormant for long stretches — boom times when the factories and fields needed more workers — it inevitably showed itself with hard times. Fear gave rise to laws that rigged the numbers in such a way that quotas favored Nordic immigrants over those from Southern and Eastern Europe. In a 1910 survey of schools, the U.S. Immigration Commission concluded that 63% of children of southern Italian descent were "retarded." They were exceeded only by the children of Polish Jews, at nearly 67%.

Schrag uncovers a long list of statesmen — conservationists, founders of the New York Zoological Society, the esteemed Sen. Henry Cabot Lodge and progressive California newspaperman V.S. McClatchy — who became rabid nativists. The more shameful of the lot pushed an American brand of eugenics that made its way to Hitler.

Now and then, a kind of consensus was achieved when the various immigrants found one immigrant to beat up on. For a good part of a century, the Chinese and Japanese — "mongrels" who would never blend in — played the role of whipping boy.

Is the Mexican the new "Oriental"? Is the recent Arizona law allowing police to demand the papers of Mexican-looking people engaged in suspicious activity a knee jerk of the same old nativism? Or is 21st century America finally stretched too thin to absorb the great press of Mexico's undocumented?

Addressing this last question, Schrag fails to fully explore the pathologies of migrant families. In the San Joaquin Valley, for instance, more than half of the high school students of Mexican descent are dropping out; large numbers are joining gangs and having children out of wedlock. Might this be a different story than the narrative of the Chinese, Armenian and Jew? Schrag doesn't say.

Quibble aside, "Not Fit for Our Society" is an important reminder that the music of anti-immigration is a tired old piece of vinyl, the same warps and scratches, over and over, sung by a babel of voices.

Arax is a former Times staff writer and the author of several books, including, most recently, "West of the West."